The presence of significant quantities of H.sub.2 S in various "sour" industrial gaseous streams poses a persistent problem. Although various procedures have been developed to remove and recover this contaminant, most such processes are deficient, for a variety of reasons.
In one cyclic method currently attracting attention, the sour gas is contacted with an aqueous polyvalent metal chelate or complex reactant system to produce solid sulfur which is recovered either prior to or subsequent to regeneration of the reactant. Preferred reactants are iron (III) complexes in which the iron (III) forms complexes with specified organic acids and derivatives thereof.
One of the disadvantages of such systems heretofore has been the inability to maintain sufficiently high concentrations of the chelate or complex to achieve efficient operation. Without sufficiently high levels of the complex, these processes are limited in their ability to handle streams containing significant quantities of H.sub.2 S. Again, the circulation of large volumes of dilute solutions to handle even moderate levels of H.sub.2 S involves significant capital and energy costs, especially in high pressure applications. Finally, degradation or decomposition of the polyvalent metal chelates represents an important cost in the process, as well as requiring measures for decomposition bleed or removal and addition of fresh solution. Even in the case of chelates such as those of nitrilotriacetic acid, ligand decomposition, over a period of time, requires attention to prevent build-up of decomposition products and consequent loss of efficiency. The invention addresses these problems, and provides a novel composition and process for the resolution thereof.